28
Quad pH/mV Amp
BNC-to-BNC cables, through which the amplified and filtered signal is
sent to the e-corder. The overall operation of the pH/mV Amp can be
better understood by referring to Figure A–1.
The
E
input is used for combination electrodes where the reference
electrode is connect to the cable shield. The electrode signal is fed to a
high input impedance amplifier of unity gain.
The
E/2
input is meant for use with ‘half cell’ electrodes (that is those
that require the use of a separate reference electrode). In these cases,
the reference electrode should be connected to the
Ref
socket. The
output of the electrometer amplifier is fed to a 3 pole, 10 Hz low pass
filter.
The
E/2
signal is protected with a actively driven shield. If you use a
half cell electrode with a coaxial cable then the shield will be extended
to the electrode. This will minimize signal leakage and allow the use of
longer cable runs (typically several metres) than would otherwise be the
case.
The pH/mV Amp output signal is fed to the e-corder for secondary
amplification and filtering.
Front Panel
Back Panel
Ref input
E input
Online indicator
E/2 input
x1
I
2
C input
I
2
C output
Electrode
signal
I
2
C interface
10 Hz
Low pass filter
x1
Isolation
Hi Z
Driven shield
To channels 2, 3 and 4
Figure A–1
Block Diagram of
Channel 1 of the Quad
pH/mV Amp
Summary of Contents for EA168
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